DE102008027261A1 - Process for improving the physico-chemical properties of biodegradable materials - Google Patents

Abstract

Process for improving the physico-chemical properties of biodegradable materials characterized in that crystallizable substances are introduced into biological raw materials.

Description

• • Verpackungsindustrie (Bioplastiken in Form von Folien, Taschen, Beuteln und Behältern)
• • Lebensmittelindustrie (in Form von Schutzschichten auf oder zwischen Lebensmitteln zum Schutz gegen mechanische Einwirkungen, sensorische Veränderungen und Austrocknung, für eine kontrollierte Migration von Inhaltsstoffen und Additiven in das Lebensmittel, für eine Regulierung der Atmosphäre des Lebensmittelsystems sowie für dekorative Elemente)
• • Agrarwirtschaft (Gewächshausfolien, Mulchfolien, Ernteverfrühungsfolien, Tunnelabdeckungen und photoselektive Filme, z. B. zum Blocken von UV-Strahlung)
• • Medizin und pharmazeutischen Industrie (Kontrollierte Wirkstofffreisetzungssysteme, Verkapselung, „Tissue Engineering”, Implantate und Behandlung von Frakturen)
• • Spielwarenindustrie (Spielzeugwaren aus Bioplastiken)
• • Textilindustrie
• • Automobilindustrie (Interieur-Bioplastik)
• • Elektronikindustrie

eingesetzt.Biodegradable materials such as foils, composites and coatings are used in a variety of ways

• • packaging industry (bioplastics in the form of films, bags, bags and containers)
• • food industry (in the form of protective layers on or between foods for protection against mechanical effects, sensory changes and dehydration, for a controlled migration of ingredients and additives into the food, for regulation of the atmosphere of the food system and for decorative elements)
• • agriculture (greenhouse films, mulch films, early harvesting films, tunnel covers and photoselective films, eg for blocking UV radiation)
• • Medical and Pharmaceutical Industry (Controlled Drug Release Systems, Encapsulation, Tissue Engineering, Implants and Treatment of Fractures)
• • toy industry (toys made of bioplastics)
• • textile industry
• • automotive industry (interior bioplastics)
• • Electronics industry

used.

To The biodegradable materials are given priority Proteins (eg casein, gelatin, collagen, wheat gluten, corn, Soy, silk and wool), polysaccharides (eg starch, cellulose, lignin and Chitin), lipids (eg vegetable oils including castor oil and animal fats produced by microorganisms or plants Polyester (eg polyhydroxyalkanoate), synthesized polyesters of monomers of biological origin (eg polylactic acid) as well as more selected Polymers (eg rubber and composites).

biodegradable Materials, in particular proteins or polysaccharides based, have compared to those prepared from conventional polymers Substances significantly reduced mechanical properties. moreover For example, protein-based materials have a high water-sensitivity, too a comparatively fast resolution of these materials Contact with liquids leads. comparatively high costs for Organic raw materials and their processing have so far led to inadequate Establishment of biodegradable products on the market. For improvement The acceptance of biodegradable materials requires selected material properties to improve and by the incorporation of crystalline substances additional Generate effects. To the influenceable mechanical properties counting in particular tensile strength, elongation at break and modulus of elasticity.

By The use of crystalline substances can make fertilizers into biodegradable films be incorporated in the case of a film decomposition in the field be released and make a conventional fertilization superfluous.

Of Furthermore, it is possible in the medical therapeutic field by the incorporation of calcium phosphate (CaP compounds) in non-toxic, physiologically harmless and in the human body degradable biomaterials the healing process of bone fractures to speed up the affected bones with protein sheets be wrapped, from which the contained calcium phosphate to the and thus the healing process actively supported. By the degradability is not additional surgical intervention is necessary to remove the slides.

Known are processes by chemical or enzymatic cross-linking certain constituents the physicochemical properties of films and coatings. Furthermore, it was investigated through composites and mixtures (so-called composites and blends) to take on the film properties. Are also known Process in which by the addition of hydrophobic substances, eg. B. by fats, oils and waxes improves the barrier properties and fluid resistance were. Furthermore, an attempt was made with a targeted ultrasound treatment the protein solution to improve the properties of biodegradable films.

These Methods are based on chemical crosslinking of components, in the often environmentally hazardous Substances (eg formaldehyde) are used. The so produced Slides do not conform to environmentally sound standards and are subject to thus a clearly limited field of application. An enzyme-catalyzed protein cross-linking is another, successfully tested method for the mechanical film properties to improve and reduce the water sensitivity. This requires however, defined reaction conditions (narrow temperature range, pH value) and a relatively high effort in the film production. In addition, the high cost of industrial enzymes is another Disadvantage.

The addition of hydrophobic substances to change the barrier properties have only a minor effect on the mechanical properties and are therefore not sufficient alone to improve the biodegradable materials desirable. An ultrasound treatment is industrially only with great effort too realize and requires a sufficiently viscous solution.

It The task was to develop a method which, on the one hand the mechanical properties (tensile strength, elongation at break and Elasticity) as well as physico-chemical properties such as permeabilities or Barrier properties liquids and gases (eg water, water vapor, oxygen, aroma, oil, etc.), solubility and sensitivity against external influences (eg liquids) and the thermal characteristic (eg glass transition temperature) of the biodegradable Material targeted to influence.

According to the invention the physical and chemical properties targeted by the use improved crystalline substances. For this purpose, selected substances, z. As potassium nitrate, urea or citric acid, crystallized within the films. By controlling process parameters (temperature and concentration) become size, shape, Distribution of crystals set within the slides. This allows the targeted influencing of the film properties. Advantageous is that the procedure with a comparatively low effort and to realize costs, since the known processes of manufacture of biodegradable materials. One Another advantage is the very flexible use of the method, since an application in both cast film production and in the production by extrusion without special effort feasible is. A particular advantage is that no additional investment in plants and processes is required and, secondly, that the costs for crystallizing substances are comparatively low.

The inventive method is characterized by easy integration into existing systems and processes, the variety of possible substances, low investment and operating costs, often changeable Parameters for targeted control of product properties as well multiple marketing opportunities of the final product.

following becomes the method according to the invention on an embodiment described in more detail.

embodiment

Biodegradable materials are produced by producing protein films and composites. The individual process steps are as a process diagram in 1 shown. A solution of distilled water or TRIS buffer pH 6-8, glycerol or PEG as plasticizer and sodium caseinate or gelatin as model proteins is homogenized using a stirred vessel in a temperature range between 30 and 100 ° C. Subsequently, the addition of the additives to be crystallized, optionally potassium nitrate, urea or citric acid in concentrations between 0.5 and 10 wt.% Is carried out. The preparation is carried out in each case with and without enzymatic crosslinking of proteins with the aid of the enzyme microbial transglutaminase (MTG).

The Enzyme-free production variant of films and composites allowed a further processing of the protein solution in a much wider Temperature range between 30 and 100 ° C. In this case, the omitted Process step 3a, the cooling the solution to 45-55 ° C.

at Use MTG are additional Procedural steps to consider. Also includes Process step 3a, the setting of the temperature to 45-55 ° C means Thermostat or alternatively by a hot plate or a water bath. After tempering, the pH of the protein solution on Values between pH 6-8 set. The enzyme MTG is then in solid or predissolved form into the protein solution given and by stirring or shaking with the protein solution homogenized.

The Further process steps are identical for the production of films and composites both with and without an MTG catalyzed enzymatic Cross-linking of the material.

To complete Homogenization of the solution by means of magnetic stirrer or imported Stabrührsystem the degassing is done by means of a centrifuge or alternatively by applying a vacuum or in the form of an ultrasonic treatment, around air pockets to avoid in the final product.

Then becomes the solution poured or sprayed into a PTFE frame or PTFE film and for 12-48 hours dried at room temperature. After this time, the removal takes place the slide, which subsequently using a desiccator at 50% rLF and at room temperature for 24-48 hours is incubated.

Claims (6)

Process for improving the physicochemical Properties of biodegradable materials characterized in that crystallizable Substances are introduced into biological raw materials. Method according to claim 1 characterized in that that substances such as potassium nitrate, urea or citric acid as to be crystallized additives. Method according to claim 1 characterized in that that after homogenization of the biological raw material at a pH of 6 to 8 in a temperature range between 30 and 100 ° C the Addition of the crystallizing additives in concentrations between 0.5 and 10 wt.% Takes place. Method according to claim 1 characterized in that that the additives to be crystallized with and without enzymatic Crosslinking of proteins using an enzyme such as microbial transglutaminase be introduced into the biological substances. Method according to one of claims 1 to 4 characterized in that without the addition of an enzyme, the protein solution after Tempering to 30-100 ° C at a pH of 6-8 Completely homogenized and then degassed, dried and incubated. Method according to one of claims 1 to 4 characterized in that in the heated to 30-100 ° C protein solution before Addition of the enzyme to 45-55 ° C tempered, the pH on 6-8 set, that Enzyme in solid or predissolved Form added and then is homogenized.